A work machine, such as a wheel loader, typically includes a lift arm assembly having an implement, such as a bucket, secured thereto. In particular, a first end of a lift arm included in the lift arm assembly is pivotally coupled to the chassis or frame of the wheel loader, whereas the bucket is pivotally coupled to a second end of the lift arm. In such a configuration, the bucket may be lifted and lowered relative to the chassis of the wheel loader, and may also be tilted relative to the lift arm.
In order to provide the motive power necessary to lift and lower the bucket relative to the chassis, and also tilt the bucket relative to the lift arm, the wheel loader typically includes a number of fluid actuators, such as hydraulic cylinders or rams. In particular, a first hydraulic cylinder or pair of cylinders is provided to lift and lower the lift arm relative to the chassis of the wheel loader. Such a cylinder (or pair of cylinders), generally referred to as a "lift cylinder", is typically coupled at a first end to the chassis of the wheel loader, and at a second end to a portion of the lift arm. Similarly, a second hydraulic cylinder or pair of cylinders is provided to tilt the bucket relative to the lift arm of the wheel loader. Such a cylinder (or pair of cylinders), generally referred to as a "tilt cylinder", is typically coupled at a first end to a portion of the lift arm of the wheel loader, and at a second end to the bucket.
In such a configuration, separate fluid or hydraulic circuits are typically provided to control the position of the cylinders. In particular, wheel loaders which have heretofore been designed typically include a first fluid circuit for controlling the lift cylinder or cylinders, and a second fluid circuit for controlling the tilt cylinder or cylinders. The use of separate fluid circuits has a number of drawbacks associated therewith. For example, separate hydraulic components must be provided for each fluid circuit thereby undesirably increasing costs associated with the wheel loader.
Moreover, in such a configuration, during certain work operations only one of the cylinders or pair of cylinders may be actuated at any given time. In particular, during a high demand (i.e. requiring a relatively large amount of hydraulic power) lift operation, the lift cylinder(s) is actuated (e.g. being extended) while the tilt cylinder(s) is deactuated (e.g. not being extended or retracted), and vice versa. Hence, during a lift operation, the tilt cylinder(s) provide no mechanical assistance to the lift cylinder(s).
What is needed therefore is an apparatus and method for controlling movement of an implement relative to a frame of a work machine which overcomes one or more of the above-mentioned drawbacks.